The influence of light and diurnal freezing temperature on the cold hardiness of winter wheat seedlings

Abstract

Seedlings of winter wheat (Triticum aestivwn cv. Rideau and Cappelle Desprez) grown on moist filter paper in petri plates in dark at low temperature increased in cold hardiness, as measured by changes in the LD50 temperatures. Rideau attained an LD50 temperature of −12 °C after 5 weeks, Cappelle Desprez, −6 °C. Exposure to light delayed the maximum hardiness by 2 weeks and increased it by 6 °C in both cultivars. Exposure to diurnal freezing temperature increased hardiness of both cultivars in the dark, and in light when excessive dehydration was prevented.Greater cold hardiness of plants of both cultivars was attained in soil in light at low temperature as compared with those in petri plates. Exposure of plants to diurnal freezing temperature maintained a higher level of hardiness after the maximum at 7 weeks than continuous low temperature without freezing. Diurnal freezing during active low temperature growth in petri plates or in soil increased hardiness of Rideau seedlings to an apparent maximum of −18 °C.